Archers shooting bows have from the beginning used limbs which flex to store energy which is transferred to an arrow when released. This energy must be transferred to the arrow in the short distance that the string moves from full draw to the start position. The early "long bow" arrow velocity was low because it could not store much energy and could not transfer it efficiently to the arrow. The more modern "recurved bow" improved on the long bow, but the instability of the limb recurve limited the amount of energy stored and the ability to put that energy back into the arrow. The recurved bow attempted to correct this but was limited by the instability of the amount of recurve. The more recurve, the greater the instability. The Turkish and Persian bows achieved outstanding results but were delicate to build and difficult to handle.
Compound bows involve complex rigging of the bowstring over pulleys carried by the bow limbs. This rigging makes it virtually impossible to unstring the bow when it is not in use. Thus, the limbs of compound bows are always under significant stress, which eventually leads to a degradation of the limb fibers and a reduction in the bow weight with time for a given setting of the bow. This requires periodic retuning of compound bows to maintain the desired performance level. Typical examples of compound bows are shown in U.S. Pat. Nos. 4,112,909, 4,340,025, 4,350,138 and 4,183,345.